Electron tube having condenser member therein



Dec. 2, 1947. w, w, ElTEL ETAL, 2,431,740

ELECTRON TUBE HAVING CONDENSER MEMBER THEREIN Filed Jan. 23, 1945 I INVENTOR Mll/am W. 5176/ Jack A. ME Cul/ough Gor on Howes ATTORNEY Patented Dec. 2, 1947 ELECTRON TUBE HAVING CONDENSER MEMBER THEREIN William'W. Eitel, Woodside, Jack A. McCullough, Millbrae, and Gordon Howes, Belmont, Calif., assignors to Eitel-McCullough, Inc.,'San Bruno, Califi, a corporation of California Application January 23, 1945, Serial No. 574,118

4 Claims. 1 Our invention'relates to a multi-unit tuba-and more particularly to'a'twi'n tetrode.

It is among the objects of our invention to provide an improved tube structure, embodying a plurality of tetrode units in a single envelope,

with an arrangement adapting the tube iorhigh frequency operation.

The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of our invention. It is to be understood that wedonot'limitourselves to this disclosure of species of our invention as we may adopt variant embodiments thereof within the scope of the claims.

- Referring to the drawing:

Figure l is a side elevational View, substantially full scale, of our tube; and

Figure 2 is a horizontal sectional view of the same take'n'in a plane indicated by line 2-2 of Figure 1. V

Figure 3 is a vertical sectional view of the tube taken in a'plane indicated by line 3-3- of Figure 2; and

Figure 4 is a'similarview taken in a plane indicated by line 4-4- of Figure 2.

In terms of broad inclusion, our improved tube comprises an envelope, a plurality of tubular anodesin the-envelope, and a'set of electrodes projecting into-each anode, each set including a cathodeand control grid and screen grid. The

conductor meanSLf-Qrthe anodes extend into one .end section of the envelope, and the conductor means forithe:sets ofielectrodes project into the other end section; the envelope sections being sealed together in a. plane transverse to the anode axes. A pair of: spaced metallic-condenser members are also preferably; provided in the envelope, one member being connected to the cathodes and the other to thescreen grids. One of these members is preferablydisposed to also function as a shield between the anodes and thelower portions of the envelope.

In greater detail, and referring to the drawing, our preferred tube structure comprises an evacuated envelope of vitreous'material, such as glass, made up of upper-andloWer'cup-shaped sections 2 and tiuse'd'together at annular seal 4 in a plane transverse tothevertical axis of the envelope. Thesesections oren'd' portions of the enenvelope along parallel vertical axes.

extend into upper section 2 of the envelope.

velope have cylindrical side walls, the top 5 of the upper section and bottom 6 of the lower section being rounded or dome-shaped for strength. Bottom wall 6 carries a centrally disposed exhaust 'tubulation which is sealed ofi at tip 1 after the tube is evacuated.

A'plurality of tetrode units-are arranged in the In the tube illustrated there are two of these units spaced on opposite sides of the tube axis. Each unit includes a tubular anode 8 of suitable metal, preferably cylindrical in shape. The lower ends of the anodes are open ended and the upper ends are preferably covered with caps 9. For convenience of manufacture cap 9 is preferably formed separately and welded to the rim of the anode,

although it may-be formed integrally with the body of the anode. Openings H in the anode structure adjacent the capped end are provided so that an operator can check alignment of the internal parts.

Conductor means for the anodes is arranged to We prefer to provide a pair of leads I? coaxial With the anodes and extending through top wall 5 at seals-l3 on tubulations Id. The anodes are supported on these leads by suitable brackets l6, preferably of conical shape having their converging ends welded to the leads and their diverging ends welded to caps-'9.

A set of electrodes is arranged to project up- Wardly into each anode, each set including a cathode il,'control grid 58 and screen grid 19. Cathode ll is preferably of the thoriated type comprising a helical filament having its upper end welded toa center-rod 2! and itslower end terminating in a depending tab'22. 'Control grid is interposed between the cathode and screen "bled.

Conductor means for'the sets of electrodes is varrangedto extendinto lower-section 3 of the 3 envelope. We prefer to provide a series of seven leads arranged in a circle and extending through bottom wall 6 at seals 26. This series includes a pair of screen grid leads 21, a pair of control grid leads 28, a pair of cathode leads 29 and a common cathode lead 3!. The several electrodes in the before mentioned sets are mounted on these leads so that all of the cathodes and grids are supported on lower section 3 of the envelope independent of section 2 which carries the anodes.

As shown in Figures 2 to 4, center rods 2| of the cathodes have outturned ends 32 welded to leads 2%. Depending filament tabs 22 are connected together by a strap 33 which in turn is welded at the center to the upturned end of an angle bracket 34, the horizontal leg of this bracket being welded to lead 3|. Thus, one end of each filament is electrically connected to a separate lead 29 while the other ends are connected to a common lead 3!. Control grids l8 are conductively supported on leads 28 by ears 36 welded to angle brackets 31. are conductively supported on leads 2? by ears 38.

In our preferred tube structure a metallic shield 39 is disposed transversely of the envelope below anodes B. This shield is mounted at the center on the upturned end of bracket 34 by collar ll, thereby supporting it with the sets of electrodes on the lower envelope section and electrically connecting it to the common cathode lead 3!. In usual operating circuits the common cathode lead is grounded, so that shield 39 is at ground potential. Apertures 42 in the shield provide openings through which the sets of electrodes project. The shield preferably has a depending annular flange 43, providing an in verted cup-shaped structure to afford maximum shielding between the anode assembly and the conductors which lead to the other electrodes.

A pair of spaced metallic condenser members are also preferably arranged in the envelope to increase the capacitance or bypass between the screen grids and ground. Shield 3!) preferably functions as one of these members, it being connected to the common cathode lead through bracket 35 as already described. The second member preferably comprises an annular metallic strip 44 spaced inwardly from annular shield flange 43. These ring-shaped members 43 and 4 are concentrically disposed about the axis of the tube. Ring 44 is conductively supported on leads 21 by brackets 15, which serves to connect the screen grids together as well as to the in ner condenser member. If the additional capacitance between the electrodes is not required,

member 54 may be eliminated.

The tube is provided with a base comprising an insulating disk A! fastened to a metallic shell 48 secured to envelope section 3 by cement 49. Central aperture 51 in disk 4! provides clearance for tip 5. A series of seven prongs 52 on the base are aligned with and secured to the oathode and grid leads. This base is of course applied as a final operation, after the envelope is evacuated.

Our improved twin tetrode structure has several advantages. One is that by incorporating two complete tetrode units in a single envelope, the physical size of each unit is proportionately small, permitting the use of closer spacings between the electrodes. Another advantage is that the particular arrangement of conductor means, with the anode leads out the top and the oathode and grid leads out the bottom, keeps all the leads reasonably short, with maximum spacing Screen grids l9 4 between the anode leads and those for the remaining electrodes. These features, among others, adapt the tube for high frequency operation. The use of tetrode units embodying screen grids, together with the shielding means and condenser members, provides a tube particularly adapted for use as an amplifier and without requiring neutralization in such circuits.

From the standpoint of tube structure, it will be appreciated that a tube of the size indicated by the drawing and having the complexity of structure inherent in the twin tetrode combination, involves some real problems in tube assembly. A major difliculty is to achieve and maintain accurate spacing and alignment between the electrodes in each of the units. Our structure is designed to simplify these problems. It has been pointed out that prior to making seal 4 the envelope is in two separate sections. At this stage anodes 8 are mounted in the envelope section 2 and the other electrodes and parts are mounted on section 3. Since the cup-shaped envelope sections are open-ended the various electrodes may be readily assembled and checked for alignment. Subsequently the two sets of electrodes are inserted into the anodes and the envelope sections fused together at seal 4.

We claim:

1. An electron tube comprising an envelope, a transverse metallic shield in the envelope havin apertures therein. tubular anodes in the envelope above the shield, conductor means for the anodes projecting into the envelope above the shield, a pair of concentric grids extending upwardly into each anode, the lower end of the outer grid in each pair registering with a shield aperture, a cathode extending upwardly within each pair of grids, conductor means for the inner grids and said cathodes projecting into the envelope below said shield, means connecting the shield to the cathodes, and a condenser member spaced from the shield and connected to the outer grids.

2. An electron tube comprising an envelope, a plurality of anodes in the envelope, a screen grid and control grid and cathode adjacent each anode, a condenser member in the envelope connected to the cathodes, and a second condenser member spaced from the first member and connected to the screen grids, one of said members extending transversely of the envelope providing a shield between end portions thereof.

3. An electron tube comprising an envelope, a tubular anode in the envelope, a screen grid and control grid extending upwardly into the anode, a cathode projecting upwardly into the anode, a condenser member in the envelope connected to the cathode, and a second condenser member spaced from the first member and connected to the screen grid, one of said members extending transversely of the envelope below the anode providing a shield between said anode and the lower end portion of the envelope.

4. An electron tube comprising an envelope, an anode supported on the upper portion of the envelope, a set of electrodes including a screen grid and control grid and cathode adjacent the anode, conductor means for said electrodes on the lower portion of the envelope, a condenser member in the envelope connected to an electrode of said set, and a second condenser member in the envelope spaced from the first member and connected to another electrode of said set, one of said members extending transversely of the envelope providing a, shield between the anode and Number Name Date said lower portion of the envelope. 2,017,549 Salzberg Oct. 15, 1935 WILLIAM W. EITEL. 2,062,302 Fay Dec. 1, 1936 JACK A. MCCULLOUGH. 2,072,637 Jobst Mar. 2, 1937 GORDON HOWES. 5 2,093,302 Beggs Sept. 14, 1937 2,125,317 Ronci Aug. 2, 1938 REFERENCES CITED 2,277,148 Ronci Mar. 24, 1942 The following references are of record in the 23581200 APlee Sept- 12, 1944 fil of this patent: 2,373,950 Eltel et a1 Apr. 17, 1945 UNITED STATES PATENTS FOREIGN PATENTS Number Name Date Number Country Date 1,815,370 Donle July 21, 1931 401,182 Great Britain Nov. 9, 1933 

